Principal Investigator / Author(s): Hausknecht, D. F.

Contractor: Science Applications, Inc.

Contract Number: A9-144-31

The California Air Resources Board is evaluating the potential benefits in air quality of an inspection/maintenance (I/M) program for heavy-duty diesel vehicles. The present study was conducted to develop information needed for this evaluation including ownership, use and maintenance practices, and alternatives for an I/M program for heavy-duty diesels.

Information on heavy-duty vehicles with diesel engines was obtained from responses to questionnaires which were mailed to a stratified sample of owners obtained from the files of the California Department of Motor Vehicles. The questionnaires addressed the areas of number, type, age, usage, and maintenance practices for diesel vehicles. Maintenance costs for parts and labor for emissions related work were also obtained.

A review of existing I/M programs in other states was conducted for the purpose of obtaining information, which could be useful in developing alternatives for a heavy-duty diesel program. Emission testing of diesels must be conducted with the engine under load to be effective. Capital costs are higher than the more common idle tests used on gasoline powered vehicles. Less costly and less adequate alternatives are also identified. A pilot program with testing of urban buses under transient or steady loading could provide the basic data necessary for a comprehensive evaluation of the benefits and costs of a larger I/M program for heavy-duty diesels.

For questions regarding this research project, including available data and progress status, contact:
Heather Choi
at (916) 322-3893